Environmental correlates of darkling beetle population size (Col. Tenebrionidae) on the Can ˜adas of Teide in Tenerife (Canary Islands) A. de los Santos, E.J. Alonso, E. Herna ´ndez & A.M. Pe ´rez Department of Ecology, Faculty of Biology, University of La Laguna, C/Astrofı´sico Fco. Sa´nchez, s/n. 38206, La Laguna, Sta. Cruz de Tenerife, Canary Islands, Spain (Received 15 January 2001, accepted 9 August 2001) The seasonal and yearly patterns in the adult population sizes of the darkling beetle Pimelia radula ascendens (Col. Tenebrionidae) were analysed in relation to climatic and biotic variables in a montane arid ecosystem of Tenerife. Pitfall trapping was conducted from 1988 to 2000, and capture–recapture technique and the Jolly–Seber method were used to estimate population sizes. The population had a long activity period, with seasonal patterns of activity from April to October. Activity densities and population sizes showed a similar seasonal pattern each year, reaching values of more than 13,000 individuals ha 1 during the summer and decreasing to 2000 per hectare before diapause. Minimum temperature is positively correlated to population size but not with activity density. During summer, darkling beetles showed a greater increase in population size than in activity density due to lower capture and recapture rates. Pimelia radula ascendens was the most abundant darkling beetle and their population size remained relatively stable over the study period, likely due to the absence of predation and competition, and to the environmental stability. # 2002 Elsevier Science Ltd. Keywords: montane environment; population stability; Insecta; overabun- dance Introduction Darkling beetles are a key element in arid and semi-arid environments because of their large population sizes and because of their roles in processing organic matter (Calkins & Kirk, 1973; Doyen & Tschinkel, 1974; Thomas & Sleeper, 1977; Slobodchikoff, 1978; Allsopp, 1980; Mordkovich & Afanas’ev, 1980; Thomas, 1983). Numerous studies have revealed the wide array of adaptive strategies of darkling beetles to arid environments (Knor, 1975; Allsopp, 1980; de los Santos et al., 1988). Darkling beetle communities may be strongly influenced by species tolerance limits in hot-dry climates (Cloudsley-Thompson & Crawford, 1970; Seely & Mitchell, 1987; Seely et al., 1988; Parmenter et al., 1989; Ward, 1991). Species must be specialized to 0140-1963/02/020287 + 22 $35.00/0 # 2002 Elsevier Science Ltd. Journal of Arid Environments (2002) 50: 287–308 doi:10.1006/jare.2001.0911, available online at http://www.idealibrary.com on